US6512377B1ExpiredUtilityPatentIndex 74
Method and apparatus for extraction of via parasitics
Est. expiryJun 29, 2021(expired)· nominal 20-yr term from priority
G01R 31/281G01R 31/2803
74
PatentIndex Score
18
Cited by
2
References
20
Claims
Abstract
The present invention relates to a via parasitics testing and extracting method for Gigabit multi-layered PCB boards. The method of the present invention is a unique test and extraction process that utilizes a TDR measurement and processes the output data therefrom externally. The testing aspect involves obtaining a TDR module waveform and obtaining a text file with output data, whereas the extraction aspect involves analysis of the data in the text file. This method can be used directly to ascertain a Gigabit via structure without the limitations that are imposed by the conventional methods discussed above, and has been theoretically proven to be highly accurate and much faster than any of the existing methods. The method of the present invention has the potential to be included as a built-in testing feature in high-speed TDR meters, and may also be used in order to design an optimized via.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A method of extracting via parasitics comprising the steps of:
a) measuring, at a measuring means, a measured time domain reflectometer (TDR) waveform characterizing said via;
b) computing, at a computing means, an analytic TDR waveform characterizing said via;
c) comparing, at a comparing means, said measured TDR waveform and said analytic TDR waveform and outputting a comparison result; and
d) extracting via parasitics from said comparison result.
2. A method according to claim 1 further comprising the steps of:
c1) verifying, from said comparison result, whether a variation between said measured TDR and said analytic TDR is within or outside a defined tolerance; and
c2) repeating steps b) and c) when step c) produces a variation that is outside said defined tolerance.
3. A method according to claim 1 wherein step a) further comprises:
regenerating a non-attenuated TDR waveform.
4. A method according to claim 3 wherein said step of regenerating comprises:
performing loss compensation calculation and frequency window shaping on said measured TDR waveform.
5. A method according to claim 1 wherein:
step a) comprises measuring a plurality of TDR waveforms based on a plurality of via models; and
step c) comprises comparing one of said measured TDR waveforms that is closest to said analytic TDR waveform with said analytic TDR waveform.
6. A method according to claim 1 wherein said step of comparing comprises carrying out an automatic collocation method.
7. A method according to claim 1 further comprising the step of:
a1) outputting data relating to said measured TDR waveform to an output file.
8. A method according to claim 7 further comprising the step of:
b1) analyzing said outputted data in order to obtain said analytic TDR waveform.
9. A method according to claim 8 wherein said step of analyzing is performed based on a set of equations characterizing said parasitics.
10. A method according to claim 9 wherein said set of equations comprises: VTDR = [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 2 ∑ j = 1 3 D i , j ] if t < 0 [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 3 ∑ j = 1 3 E i , j ] if 0 ≤ t < tr [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 3 ∑ j = 1 3 F i , j ] if tr ≤ t
where “−” is employed for the π-shape structure, and “+” is employed for the T-shape structure, and the values of D i,j , E i,j and F i,j in the equations above being defined by: D 1 , j = p j ( q j ) 2 · 2 · π · fc · t · [ 1 2 · π · fc · ( 1 - - 2 · π · fc · tr ) - 1 q j + 2 · π · fc · [ 1 - - ( q j + 2 · π · fc ) · tr ] ]
D 2 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · ( 1 - - q j · tr ) · 2 · π · fc · ( t - tr )
E 1 , j = p j ( q j ) 2 · [ 1 2 · π · fc · [ 1 - - 2 · π · fc · ( tr - t ) ] - 1 q j + 2 · π · fc · - q j · t · [ 1 - - ( q j + 2 · π · fc ) · ( tr - t ) ] ]
E 2 , j = p j ( q j ) 2 · [ - 1 2 · π · fc · ( - 2 · π · fc · t - 1 ) - 1 q j - 2 · π · fc · - q j t · [ ( q j - 2 · π · fc ) · t - 1 ] ]
E 3 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · - q j · t ( q j · tr - 1 ) - ( q j + 2 · π · fc ) · ( tr - t )
F 1 , j = p j ( q j ) 2 · - 2 · π · fc · t · [ - 1 2 · π · fc · ( 1 - 2 · π · fc · tr ) - 1 q j - 2 · π · fc · [ 1 - - ( q j - 2 · π · fc ) · tr ] ]
F 2 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · - q j · t ( q j · tr - 1 )
F 3 , j = p j ( q j ) 2 · 1 q j - 2 · π · fc · ( q j · tr - 1 ) · [ - ( q j - 2 · π · fc ) · tr · - 2 · π · fc · t - - q j · t ]
where the values p 1 , p 2 , p 3 , q 1 , q 2 , q 3 are functions of C 1 , L, C 2 , Z 0 or L 1 , C, L 2 , Z 0 , which may be expressed as: p j = [ a1 · ( q j ) 2 - a2 · q j + a3 h ] · d j d 1 = 1 d 2 = - ( q 1 - q 3 ) q 2 - q 3 d 3 = q 1 - q 2 q 2 - q 3 h = ( q 1 ) 2 - q 1 · ( q 2 + q 3 ) + q 2 · q 3 where ,
q 1 = - ( S + T - b1 3 ) q 2 = - [ - 1 2 · ( S + T ) - 1 3 · b1 + 1 2 · i · 3 · ( S - T ) ] q 3 = - [ - 1 2 · ( S + T ) - 1 3 · b1 - 1 2 · i · 3 · ( S - T ) ] and where ,
S = ( RR + QQ 3 + RR 2 ) 1 3 T = ( RR - QQ 3 + RR 2 ) 1 3 RR = 9 · b1 · b2 - 27 · b3 - 2 · ( b1 ) 3 54 QQ = 3 · b2 - ( b1 ) 2 9 and where , for the π - shape structure ,
a1 = 1 C1 · Z0 a2 = 1 C1 · C2 · ( Z0 ) 2 a3 = 1 L · C1 · C2 · Z0 b1 = C1 + C2 C1 · C2 · Z0 b2 = ( C1 + C2 ) · ( Z0 ) 2 + L L · C1 · C2 · ( Z0 ) 2 b3 = 2 L · C1 · C2 · Z0 whereas for the T - shape structure : a1 = Z0 L1 a2 = ( Z0 ) 2 L1 · L2 a3 = Z0 C · L1 · L2 b1 = ( L1 + L2 ) · Z0 L1 · L2 b2 = L1 + L2 + C · ( Z0 ) 2 C · L1 · L2 b3 = 2 · Z0 C · L1 · L2
and where the total signed TDR voltage-versus-time area, S, is derived and represented by: S_x = - 2 · Δ V · ∑ j = 1 3 p j ( q j ) 2 = L · Δ V 2 · Z0 - ( C1 + C2 ) · Δ V · Z0 2 or S_T = 2 · Δ V · ∑ j = 1 3 p j ( p j ) 2 = ( L1 + L2 ) · Δ V 2 · Z0 - C · Δ V · Z0 2 .
11. A method according to claim 1 comprising, before said step of obtaining, the step of launching a step function.
12. An apparatus for extracting via parasitics comprising:
measuring means for obtaining a time domain reflectometer (TDR) waveform characterizing said via;
computing means for computing an analytic TDR waveform characterizing said via;
comparing means for comparing said measured TDR waveform and said analytic TDR waveform and for outputting a comparison result; and
extracting means for extracting via parasitics from said comparison result.
13. An apparatus according to claim 12 wherein said measuring means comprises:
a time domain reflectometer; and
a digital oscilloscope.
14. An apparatus according to claim 13 wherein said digital oscilloscope measures values selected from the group of: amplitude, rise time and time sampling step.
15. An apparatus according to claim 12 further comprising a coaxial cable used to connect a launch port of the measuring means to a board having said via.
16. An apparatus according to claim 12 further comprising means for outputting said output data as a text file including discretized time and voltages.
17. An apparatus according to claim 12 wherein said apparatus is a high-speed TDR meter.
18. A method of designing a via comprising the steps of:
a) computing, at a computing means, a first time domain reflectometer (TDR) waveform of a proposed via design, said first TDR waveform being obtained by analytical or numerical method calculation;
b) comparing, at a comparing means, said first TDR waveform with a second TDR waveform having desired characteristics for said via and outputting a comparison result;
c) verifying, from said comparison result, whether a variation between said first TDR waveform and said second TDR waveform is within or outside a defined tolerance;
d) if necessary, repeating steps a) and b) until step c) produces a variation that is within said defined tolerance; and
e) extracting via parasitics from said comparison result in order to design the via therefrom.
19. A method according to claim 18 wherein said first TDR waveform is obtained based on a set of equations characterizing said parasitics.
20. A method according to claim 19 wherein said set of equations comprises: VTDR = [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 2 ∑ j = 1 3 D i , j ] if t < 0 [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 3 ∑ j = 1 3 E i , j ] if 0 ≤ t < tr [ ∓ ( 2 · Δ V · π · fc tr ) · ∑ i = 1 3 ∑ j = 1 3 F i , j ] if tr ≤ t
where “−” is employed for the π-shape structure, and “+” is employed for the T-shape structure, and the values of D i,j , E i,j and F i,j in the equations above being defined by: D 1 , j = p j ( q j ) 2 · 2 · π · fc · t · [ 1 2 · π · fc · ( 1 - - 2 · π · fc · tr ) - 1 q j + 2 · π · fc · [ 1 - - ( q j + 2 · π · fc ) · tr ] ]
D 2 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · ( 1 - - q j · tr ) · 2 · π · fc · ( t - tr )
E 1 , j = p j ( q j ) 2 · [ 1 2 · π · fc · [ 1 - - 2 · π · fc · ( tr - t ) ] - 1 q j + 2 · π · fc · - q j · t · [ 1 - - ( q j + 2 · π · fc ) · ( tr - t ) ] ]
E 2 , j = p j ( q j ) 2 · [ - 1 2 · π · fc · ( - 2 · π · fc · t - 1 ) - 1 q j - 2 · π · fc · - q j t · [ ( q j - 2 · π · fc ) · t - 1 ] ]
E 3 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · - q j · t ( q j · tr - 1 ) - ( q j + 2 · π · fc ) · ( tr - t )
F 1 , j = p j ( q j ) 2 · - 2 · π · fc · t · [ - 1 2 · π · fc · ( 1 - 2 · π · fc · tr ) - 1 q j - 2 · π · fc · [ 1 - - ( q j - 2 · π · fc ) · tr ] ]
F 2 , j = p j ( q j ) 2 · 1 q j + 2 · π · fc · - q j · t ( q j · tr - 1 )
F 3 , j = p j ( q j ) 2 · 1 q j - 2 · π · fc · ( q j · tr - 1 ) · [ - ( q j - 2 · π · fc ) · tr · - 2 · π · fc · t - - q j · t ]
where the values p 1 , p 2 , p 3 , q 1 , q 2 , q 3 are functions of C 1 , L, C 2 , Z 0 or L 1 , C, L 2 , Z 0 , which may be expressed as: p j = [ a1 · ( q j ) 2 - a2 · q j + a3 h ] · d j d 1 = 1 d 2 = - ( q 1 - q 3 ) q 2 - q 3 d 3 = q 1 - q 2 q 2 - q 3 h = ( q 1 ) 2 - q 1 · ( q 2 + q 3 ) + q 2 · q 3 where ,
q 1 = - ( S + T - b1 3 ) q 2 = - [ - 1 2 · ( S + T ) - 1 3 · b1 + 1 2 · i · 3 · ( S - T ) ] q 3 = - [ - 1 2 · ( S + T ) - 1 3 · b1 - 1 2 · i · 3 · ( S - T ) ] and where ,
S = ( RR + QQ 3 + RR 2 ) 1 3 T = ( RR - QQ 3 + RR 2 ) 1 3 RR = 9 · b1 · b2 - 27 · b3 - 2 · ( b1 ) 3 54 QQ = 3 · b2 - ( b1 ) 2 9 and where , for the π - shape structure ,
a1 = 1 C1 · Z0 a2 = 1 C1 · C2 · ( Z0 ) 2 a3 = 1 L · C1 · C2 · Z0 b1 = C1 + C2 C1 · C2 · Z0 b2 = ( C1 + C2 ) · ( Z0 ) 2 + L L · C1 · C2 · ( Z0 ) 2 b3 = 2 L · C1 · C2 · Z0 whereas for the T - shape structure : a1 = Z0 L1 a2 = ( Z0 ) 2 L1 · L2 a3 = Z0 C · L1 · L2 b1 = ( L1 + L2 ) · Z0 L1 · L2 b2 = L1 + L2 + C · ( Z0 ) 2 C · L1 · L2 b3 = 2 · Z0 C · L1 · L2
and where the total signed TDR voltage-versus-time area, S, is derived and represented by: S_x = - 2 · Δ V · ∑ j = 1 3 p j ( q j ) 2 = L · Δ V 2 · Z0 - ( C1 + C2 ) · Δ V · Z0 2 or S_T = 2 · Δ V · ∑ j = 1 3 p j ( p j ) 2 = ( L1 + L2 ) · Δ V 2 · Z0 - C · Δ V · Z0 2 .Cited by (0)
No later patents cite this yet.
References (0)
No backward citations on record.